An adaptive cruise control system (ACC) in a vehicle measures the distance to a vehicle in front. This distance information is used to modify the adaptive cruise control in such a way that the distance to the vehicle in front is never less than a predetermined value.
When a vehicle in front is driving more slowly than the vehicle in question, the adaptive cruise control must ensure that the vehicle in question is braked. This can be carried out in a number of ways. For example, the fuel supply to the motor of the vehicle in question can be shut off completely so that the vehicle slows down. If all the fuel is shut off and additional braking is required, this can be carried out using the vehicle's service brake. A disadvantage of using the vehicle's service brake is that the service brake is a friction brake with a tendency to wear. For this reason, particularly on heavy goods vehicles, so-called auxiliary brakes are often used. Examples of auxiliary brakes are motor compression brakes and retarders. When an auxiliary brake is arranged in the vehicle's motor or between the motor and the gearbox, the gear selection is of great significance for what braking force is applied to the vehicle's driving wheels.
A vehicle with cruise control is shown in U.S. Pat. No. 6,076,622 and in which the cruise control can also control the gear selection and auxiliary braking. A problem with this solution is that the gear selection and the auxiliary braking cannot be optimized with regard to future topography. For example, at the start of a long steep down-grade, a sufficiently low gear will not be selected, which eventually leads to the auxiliary braking becoming insufficient at a relatively early stage on the gradient and it becoming necessary for additional braking to be carried out with the service brake in order to avoid driving into the vehicle in front.
A vehicle with cruise control is known through FR 2813397, where a control system with a navigation system using position determination (GPS, Global Positioning System) calculates in advance the highest and lowest points, that is the transitions where an uphill gradient changes to a downhill gradient or vice versa, for the immediately imminent road on which the vehicle is being driven. The distance to a vehicle in front is optimized by the control system controlling the acceleration and braking with the vehicle's service brake, taking into account the highest and lowest points on the road on which the vehicle is being driven. A problem with this solution is that the most favorable braking sequence can not be selected taking into account brake wear and gear selection. In addition, the future topography, in accordance with which the cruise control carries out the control, is greatly simplified. Only the transitions in gradient along the road on which the vehicle is being driven are calculated. The topography between the transitions in gradient is not taken into account.
SE 0103630-0 shows a known motordriven vehicle with cruise control, where a control system calculates future topography using a navigation system with position determination (GPS, Global Positioning System) or by extrapolation. By means of simulation, the control system selects an acceleration and/or retardation that is matched to the future topography, by controlling the acceleration and braking. A problem with this solution is that the most favorable braking sequence cannot be selected which takes into account brake wear, gear selection and distance to the vehicle in front.
Against the background of the above, the task of the invention is thus to make it possible to control a vehicle's braking sequence in a more optimal way, in a vehicle with cruise control of the ACC type (Adaptive Cruise Control), with acceleration function, brake function and distance measurement to the vehicle in front.